1. Field of the Invention
The present invention relates to a recording medium driving device which is classified as a so-called front loading type wherein an information recording medium is mounted on a mounting member jutting out toward the front surface of a device body, and the recording or reproduction is effected by putting this mounting member into the device body, and more particularly, to a recording medium driving device suitable for an optical disk driving device.
2. Description of the Prior Art
In an optical disk driving device, there is broadly adopted a method in which an optical disk is mounted on a tray that protrudes toward the front surface of a device body, and the optical disk together with the tray is led into the device body so as to effect the recording and reproduction. As one example, the present applicant disclosed an invention in the specification of Japanese Patent Application No. 233990/l985.
The outline of a conventional optical disk driving device relative to the above-described invention will hereinafter be described with reference to the drawings.
In FIGS. 26 to 29 inclusive, the optical disk driving device substantially consists of: a chassis 101; a covering member 103 equipped with a clamper 102 and axially so supported as to be pivotable relative to the chassis 101; a tray 104 mounted with an optical disk; and a tray driving mechanism 105 for leading the tray into the chassis 101 and arranging for the tray 104 to jut out from the chassis 101.
The tray driving mechanism 105 is constituted by: a gear train 107 engaging with a rack 106 which moves integrally with the tray 104; and a motor by which to drive the gear train 107, this tray driving mechanism 105 being provided on the side of feeding out the tray beneath the chassis 101. Freely rotatable rollers 108, 109 are axially supported by the rack 106. The externally disposed roller 109 is arranged to roll on the upper surface of the chassis 101; and the internally disposed roller 109 is likewise arranged to roll on the lower surface of the covering member 103. A supporting spindle 110 which axially and rotatably retains the rollers 108, 109 is attached to the above-mentioned rack 106 so that the supporting spindle is movable within a slot 111 formed in the side surface of the tray 104, this supporting spindle 110 being always biased toward the center of the tray 104 by a spring 112.
With this arrangement, when the motor, as illustrated in FIG. 26, rotates from a state in which the tray 104 is protruding (an inject-state) in the direction of loading, the rack, as shown in FIG. 27, moves in the direction indicated by an arrowhead D, and the tray 104 also moves in the same direction indicated by the arrowhead D by of the spring 112. When the tray 104 is led to a loading position shown in FIG. 28, the tray 104 impinges upon a predetermined position of the chassis 101 and is hindered from moving in the direction of the arrowhead D. As a result, the rack 106 alone moves in the direction pointed by the arrowhead D, resisting the resilient force of the spring 112. In this process, the covering member 103 descends along the slope of a cam groove 113, and the descent of the covering member 103 is completed just when the above-described supporting spindle 110 reaches the end portion of the slot 111. At this time, an optical disk 114 is clamped between the clamper 102 and a turn table 115, thereby effecting a loading operation of the optical disk with respect to the turn table 115.
At the eject-time, the tray 104 is rendered protruding by the above-described steps in reversed order. After completing the projection of the tray, the optical disk 114 can be taken up from the tray 104.
In the thus constituted optical disk driving device, in case that the tray 104 impinges upon any obstacles such as a human body when the tray 104 juts out, and if the tray 104 continues its protruding action, the motor is likely to be damaged when it is loaded. In addition, some of the gears of the gear train 107 or the rack 106 are broken off, thereby probably bringing about an undesirable condition in the operation thereof.
According to a conventional method, in order to steer clear of this situation an electrical control means is employed for inverting the motor by detecting electrical variations created when the load is applied on the motor. This method is effective especially in a motor having a large diameter to produce large torque. However, this method is attended with the following problems. Videlicet, the costs of manufacturing the motor increase in proportion as the motor becomes large in size, whereby it is inevitably difficult to reduce the driving device in thickness. If the diameter of the motor is small, the driving torque will decrease, so that it is required to utilize a gear train the reduction ratio of which is large. Provided that the reduction ratio is large, variations in load of the motor is unlikely to be present as compared with a gear train whose reduction ratio is small. Consequently, an electrical sensor with high accuracy is needed for detecting such variations and effecting the electrical control, thereby increasing the cost of production.